Originally Posted by
beng1
The pipe used for gas-pipe in homes is very similar to rigid electrical conduit. Both are threaded on construction sites using the same equipment, usually Ridgid brand pipe cutting and threading equipment. This pipe has a thick enough wall to allow for the cutting of threads so it can be screwed together with threaded couplings. In my career as a union-electrician, I have run tons and tons of rigid electrical conduit, and have also used the same tools used for it to run gaspipe in some homes.
Gas pipe and rigid electrical conduit are low-carbon steel, they can be bent with a hand bender, usually gas pipe is not bent in installations, but electrical conduit always is bent because it saves money on expensive fittings and also because wire has to be pulled through it and it needs a radius bend to make that possible.
There is also thin-wall electrical tubing which is also low-carbon and easily bent, but it's thin walls would make it unsuitable for structural use as in a bicycle because it would probably bend very easily just from the pedaling force on a bottom-bracket.
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The tubing used in constructing bicycle frames of lugged-frame bikes is high carbon steel, so it has a spring-like property to it, as springs themselves are made of spring-steel, which is high-carbon steel hardened to the degree where it will spring and not break. Moving up the ladder would be chrome-moly frame tubing, which has chromium and molybdenum added to the high-carbon steel, 4130 is a chrome-moly steel.
Lugged-frame bikes with high-carbon or chromoly frames will typically have non-butted tubes with a straight wall thickness close to 1 millimeter, or about .039". A butted alloy steel frame will have frame tubes that are close to one-mm at the ends and in the middle can be almost half that thickness.
Today I measured the wall-thickness of a 40+ year-old Huffy ten-speed frame I had cut up for parts with a vernier caliper and it was a solid .75" thick, almost two-mm or almost twice as thick and heavy as the tubing used on a high-end lugged frame bicycle. It is easy to see why a ten-speed frame made of tubing this thick would weigh more than twice as much as a high quality Columbus SL frame, which is why my Columbus framed Schwinn supersport weighs about ten pounds less than my Huffy ten-speed bike.
I also used to work in a metal distribution center/fab shop, employed as a fabricator/welder/machinist, and had my hands on a lot of different types of steel tubing and countless other types of metal products, which gives me some insight into how bicycles are fabricated.
So when someone tells me a bicycle is made of gas-pipe, I have a very real-world idea and expectation for what it's frame material should be, and that would be very heavy wall low-carbon steel. Not thick enough to be threaded, because the last piece of rigid electrical conduit I measured had a .150" wall, twice as thick as a Huffy frame tube, but it's frame should have tubing with a wall thickness about twice that of most lugged bikes, and be about twice as heavy as the frame of any higher priced bicycle with chromoly straight gauge or butted tubing.
Great information. Thanks. I don't believe there's been an earlier post by anyone on Bike Forums that discussed the characteristics of low-carbon versus high-carbon steel in bike fabrication. Certainly not in anything like this depth. There's a lot to digest here.
On this topic, I've always wondered whether the first steel bikes were literally built with gas pipe, i.e., with pipe that was conveniently available for use in bike fabrication because it was already being manufactured in great quantities for use in the distribution of gas throughout towns and cities for use in commercial and residential properties, in street lighting, etc. (A standard dimension for the outer diameter of both gas pipes and bike tubing in the 19th century was one inch, I believe.) So I just did a search and found this:
"
By the early 1800's, Paris and London had installed gas lamps along their streets. The added light increased accessibility and demand for nighttime activities, changing the nighttime culture from one of shutting oneself in to going out and socializing with others."
Coincidentally, I learned only yesterday that the first patent for a more or less modern bicycle (crank drive, rotating pedals rather than stationary pegs, etc.) was issued in 1866, in my home town of New Haven.
I guess that explains why bike manufacturers are said to use gas pipe. If bikes had come first, would my gas stove use bike pipes?